Production of nitrogen.



M. SHOELD.

PRODUCTION OF NITROGEN.

APPLICATION FILED MAR. 6. 1918.

1,287,472. Patented Dec.10, 1918.

MARK SHOELD, OF CHICAGO, ILLINOIS,

PATENT OFFICE.

ASSIGN OR TO ARMOUR FERTILIZER WORKS, OF

CHICAGO, ILLINOIS, A CORPORATION OF NEW JERSEY.

PRODUCTION OF NITROGEN.

Specification of Letters Patent.

Patented Dec. 10, 1918.

Application flied March 6, 1918, Serial No. 220,676.

To all 'whom it may concern:

Be it known that I, MARK SHoELn a subject of the King of Sweden, residing at Chicago, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in the Production of Nimain or principal product and the nitrogenthe supplemental or subsidiary gas. Considering the nitrogen as the particularly desirable gas to be produced, the leading and prime objects of the invention are the provision of a method for its supply which shall be continuous in its operation, which shall be economical in its performance, and which shall employ the most ordinary materials or ingredients for its carrying out.

In the preferred method air and fuel are the only ingredients employed and actually consumed and these, of course, are readily available and comparatively inexpensive.

An alkali carbonate solution is also employed in connection with the separation of the carbon-dioxid from the nitrogen but inasmuch as such solution, after its absorption of the carbon-dioxid, is automatically restored to its original condition and is, therefore, used continuously, it is not a source of expense, except to the small extent required to keep the solution up to the desired strength.

In order that those skilled in this art may have a full and complete understanding of the invention and its various advantages, I have illustrated preferred embodiments thereof in the accompanying drawin forming a part of this specification, and t roughout the views of which like reference characters refer to the same parts.

In this drawing Figure 1 illustrates the apparatus for carrying out one method, and

Fig. 2 a modified apparatus used in connection with a slightly different process.

The apparatus used for the performance of the preferred process is illustrated in Fig. 1 and comprises a furnace substantially like a producer furnace except that no steam is used. Such furnace contains a bed 11 ofheated coke, the required temperature of dioxid without moisture.

which is maintained without the employment of extraneous heat, by reason of the chemical reaction occurring therein, and such body of fuel may be continuously or intermittently replenished in any approved and convenient manner. this furnace, and below its bed of. fuel, air is fed or delivered under'pressure by a compressor or blower .12 in quantity suflicient to convert the oxygen of the air into carbon-dioxid, whereby the product of such furnace constitutes a gaseous mixture of nitrogen and carbon-dioxid, with possibly a small or practically negligible per cent. of carbon monoxid whose presence in the nitrogen product is not all detrimental when used for some purposes, as, for example, where the nitrogen is availed of in a nitriding furnace for the production of aluminum nitrid.

After passing through a cooler 13, such gaseous mixture is delivered to the lower portion of a scrubber or tower 14 of the usual construction, packed with coke or other suitable material 15. I In this appliance, the carbon-dioxid gas is absorbed or separated from the nitrogen of the gaseous mixture, permitting the nitrogen to pass to a cooler 16, where the moisture thereof is condensed, the nitrogen free from moisture, but with possibly a trace of carbon monoxid, issuing from the discharge-pipe 17. This carbondioxid absorption is accomplished by delivering into the scrubber at the top a solution of potassium carbonate which, by coming into intimate contact with the carbondioxid of the mixture, absorbs the former and is itself converted into potassium bi-v carbonate solution which flows through a pipe 19 and through one coil 20 of a heatexchange appliance 21 to a tank 22 maintained at boiling temperature by the application of a small. amount of external heat indicated at 23.

Such heating of the potassium bicarbonate solution drives ofi or expels the car bon-dioxid previously absorbed and steam, which, upon passing through a cooler or condenser 24 issues therefrom through the tube or pipe 25 as practically pure carbontwo desired dioxid. c

When the carbon-dioxid is driven off from the potassium bicarbonate solution, as exproducts, nitrogen, and carbon- Through- Thus we have the 4 plained, the latter is reconverted into a solution of potassium carbonate and suchhot solution, by a pump :26, is forced through the other or companion coil 27 of the heatchanger 21 and through a cooler 28 to the pipe 18 and to the scrubber again.

Thus we seev that the process is continuous, consuming only air and fuel, and producing the two dissimilar gases, either of which may be the required product and the other the byproduct depending upon circumstances.

The furnace 10, although somewhat like a producer furnace differs therefrom in its action and results. In the present process the object is to remove the oxygen from the air so as to leave the desired nitrogen and to remove it in such a way that it can be readily and economically sepa 'ated from the nitrogen. leaving the latter substantially pure and practically free from diluent gases. In a. producer furnace the object is to produce as much carbon monoxid as possible, whereas with the present furnace the purpose is to form carbon-dioxid, the object being to get rid of the objectionable oxygen, or, stated differently, the function of this furnace is to so combine the oxygen with the carbon that it can be readily separated from the nitrogen later on in the process.

To those skilled in this art it will be apparent that one or more of the coolers or condensers may be omitted, the pi iing itself in some cases constituting a su cicnt cooler. It is necessary, however, to absorb the carbon-dioxid under cool conditions and to expel it from the solution at a higher heat as specified. It is not required that the heated potassium carbonate solution should be used to raise the temperature of the incoming cool potassium bicarbonate solution, but this, of course, is a feature of economy which re duces the amount of heat necessary to be ap-.

plied to the tank 22, as well as securing a desired reduction of temperature of the hotter solution.

In the process presented above, any suitable alkali carbonate solution may be used,

but potassium carbonate solution is preferable to sodium carbonate solution because of the different degrees of solubility of the two carbonates. Caustic soda or sodium hydroxid may be employed, however, in a somewhat different manner. In such case, a caustic soda solution absorbs the carbon-dioxid in the scrubber, the solution being thereby converted into a solution of sodium earbonquires the use of lime and is, therefore, under ordinary. circumstances, not to be preferred to the other method.

\Vhile I have, herein set forth only two methods representing desirable ways of taking advantage of this invention, it is to be understood that the latter is not limited and restricted to the precise and exact steps presented nor to the apparatus illustrated and described, because both of these may be modified in many minor respects without departure from the heart and substance of the invention and without the sacrifice of any of its substantial benefits and advantages.

I claim:

1. The process of supplying nitrogen and carbon -dioxid consisting in producing a gaseous mixture. of nitrogen and carbon-dioxid, scrubbing such mixture for the removal of the carbon-dioxid therefrom with a chemical solution capable of reacting with said carbon-dioxid thus freeing-the nitrogen, then by heat driving Off the carbon-dioxid from such modified solution, restoring the latter to its original condition, and transferring the heat of said restored solution to the modified solution, substantially as described.

2. The process of producing nitrogen and. earbon-dioxid consisting in supplying air in such quantity to a body of heated carbon as to produce a gaseous mixture composed practically entirely. of nitrogen and carbon-dioxid, scrubbing such mixture for the removal of the earbon-dioxid therefrom with an alkili carbonate solution capable of reacting with said carbon dioxid thus freeing the nitrogen, then by heat driving off the carbon-dioxid from such modified solution restoring the latter to its original condition, and transferring the heat of said restored solution to the modified solution, substantially as described.

MARK SHOELD. 

